<%@ page language="java" pageEncoding="UTF-8"%>
<%@ page contentType="image/jpeg"  import="java.awt.*,java.awt.image.*,java.util.*,javax.imageio.*" %>
<%!
    public Color getColor(){
    Random random = new Random();
    int r = random.nextInt(256);//0-255
    int g = random.nextInt(256);
    int b = random.nextInt(256);
    return new Color(r,g,b);
}
public String getNum(){
    String str = "";
    Random random = new Random();
    for(int i=0;i<4;i++){
        str += random.nextInt(10);//0-9
    }
    return str;
}
%>
<%
response.setHeader("pragma", "mo-cache");
response.setHeader("cache-control", "no-cache");
response.setDateHeader("expires", 0);

BufferedImage image = new BufferedImage(80,30,BufferedImage.TYPE_INT_RGB);

Graphics g = image.getGraphics();
g.setColor(new Color(200,200,200));
g.fillRect(0,0,80,30);

for (int i = 0; i < 30; i++) {
    Random random = new Random();
    int x = random.nextInt(80);
    int y = random.nextInt(30);
    int xl = random.nextInt(x+10);
    int yl = random.nextInt(y+10);
    g.setColor(getColor());
    g.drawLine(x, y, x + xl, y + yl);
}

g.setFont(new Font("serif", Font.BOLD,16));
g.setColor(Color.BLACK);
String checkNum = getNum();//"2525"

StringBuffer sb = new StringBuffer();
for(int i=0;i<checkNum.length();i++){
    sb.append(checkNum.charAt(i)+" ");//"2 5 2 5"
}
g.drawString(sb.toString(),15,20);

session.setAttribute("CHECKNUM",checkNum);//2525

ImageIO.write(image,"jpeg",response.getOutputStream());
out.clear();
out = pageContext.pushBody();
%>